Another Null Reference Exception

I am getting a null reference to the class partHull in the following code: (this is not all of it, only the important parts)

 public class partHull extends UnityEngine.MonoBehaviour
 {
     public var position            :int;
     public var isPartUsed         :boolean = false;
     private var jaska            :GameObject = Resources.Load("Alus");
     private var partLoc            :Vector3;
 
     public function partHull(num : int, vector : Vector3)
     {
         position = num;
         partLoc = vector;
     }
     public function guiLoop()
     {
         if (GUI.Button(Rect(10,170,50,30),"Plus")) {
             if (!isPartUsed) {
                 partHullInstance = Instantiate(jaska, partLoc, transform.rotation);
                 isPartUsed = true;
                 partHullInstance.AddComponent("FixedJoint");
                 partHullInstance.GetComponent("FixedJoint").connectedBody = rigidbody;
                 partHullInstance.GetComponent("FixedJoint").breakForce = 5;
                 partHullInstance.GetComponent("FixedJoint").breakTorque = 5;
             } else {
                 Destroy(partHullInstance);
                 isPartUsed = false;
 }    }    }    }
 
 paikka = new Vector3(-3,-3,0.75);
 var hull = gameObject.GetComponent(partHull);
 hull.partHull(1,paikka);
 
 function OnGUI () {
 hull.guiLoop();
 }

The line giving me problems is hull.guiLoop(); It should be noted that hull is successfully referenced once in hull.partHull(1,paikka);

I have no idea what is wrong, and I am new to js so help is appreciated.